A mobile node is an Internet-connected device whose location and point of attachment to the Internet may frequently be changed. This kind of node is often a cellular telephone or handheld or laptop computer, although a mobile node can also be a router. Special support is required to maintain Internet connections for a mobile node as it moves from one network or subnet to another, because traditional Internet routing assumes a device will always have the same IP address. Therefore, using standard routing procedures, a mobile user would have to change the device's IP address each time they connected through another network or subnet.
Since mobility and ease of connection are crucial considerations for mobile device users, organizations that want to promote mobile communications are putting a great deal of effort into making mobile connection and uncomplicated for the user. The Internet Engineering Task Force (IETF) Mobile IP working group has developed several standards or proposed standards to address these needs, including Mobile IP and later enhancements, Mobile IP version 6 (MIPv6) and Hierarchical Mobile IP version 6 (HMIPv6).